My other thought is just scrap that idea, and instead do an internal support cage of some type-so you've got a couple bars below the rack rails, and some legs that run down to the wheel wells/truck bed? In that situation your topper isn't really doing anything other than acting like a fiberglass washer for your RTT support system, and keeping the load from swaying side to side.... but all the load is transferred down to the truck bed. I kind of like this idea better.

I swear an internal support system was available from some manufacturer. I thought it was Rhino-Rack but can't find it in their on-line catalog. I have a hard copy catalog at home and will check it tonight.

I poked around Expedition Portal last night and found one guy who say his fiberglass cracking, another who said just a topper was causing the bed to spread.

Were those ARE toppers? I found a lot of happy ARE/RTT users on there and none had issues. Plus I'm thinking that the metal 5 foot beds on our rigs would be more rigid than longer beds or composite beds on later model Tacos. so maybe the spreading is a non-issue.

At any rate, I'm going to try it and I'll let you know how it holds up. I was hoping to get the ARE and tent mounted up before our Arizona/Utah trip later this month, but I will have to special order the topper with all the features I want and they said 3 weeks.

You know, the internal skeleton idea, that is exactly how a WilderNest is built... There is a molded in steel frame that is pretty strong and does not flex much normally. In fact it only deflects about two inches when it must hold up the weight of a truck, so a few hundred lbs is no prob.

Yes! that Rhino design, or the ARB one, that's what I'm talking about. Looks like the ARB one mounts to the side of the bed while the Rhino one goes all the way down? but the Rhino one just pokes through the topper with a big hole.. I think we can do better, but I like the approach..

Seems like all you need is a rib that follows the contour of the inside of the shell that runs from bed rail to bed rail under each rack cross member. I'm seeing 3/4" tubing, a bender and welded plates on each end. Very much like a internal roll cage that fits snug under the shell. Tie the internal ribs to the topper ceiling and to the Yakima or Thule feet on the roof, with, I dunno, u-bolts or maybe tabs on the ribs. The fiberglass in a topper is pretty strong and the goal is just to minimize flex to keep it from cracking.

If it was me I would just mold in metal or wood reinforcement into the inside and ceiling of the fiberglass, but I could care less about appearance. You can see part of the 'Nest frame in this photo. There are 4 rectangular tubes, one at each corner, connected along the side with horizontal members over the windows. The whole thing is then covered in structural fiberglass.

Yeah now you're talking Dave, bent 3/4" tubing with some feet would be sweet, heck I'd even settle for miter cut 1" square... the front legs would just rest on the wheel wells, the ones in back would tuck nicely between the windows on the way down.